Spiral strip accumulator and method

ABSTRACT

A compact strip accumulator and method wherein a series of guide rollers are arranged to define an archimedean spiral having a plurality of convolutions, the strip to be accumulated being fed to the inside of the outermost convolution of the spiral, a reverse loop formed in the strip so that its leading end extends in the opposite direction and passes to the outside of the outermost convolution of the spiral, the reverse loop, as strip is fed into the spiral, traveling inwardly in a spiral path between the rollers defining consecutive convolutions of the spiral, thereby building up sets of convolutions of strip of opposite hand interconnected by said reverse loop; and as the strip is removed, the reverse loop travels in the same spiral path in the opposite direction, i.e., outwardly, thereby reducing the number of sets of convolutions of opposite hand and hence the quantity of accumulated strip.

United States Patent 1191 Primary Examiner-John W. Huckert Assistant Examiner-Edward J. McCarthy Attorne'y, Agent, or Firm-John W. Melville; Albert E. Strasser; Stanley H. Foster La Tour Apr. 23, 1974 SPIRAL STRIP ACCUMULATOR AND [5 7] ABSTRACT METHOD [75] Inventor: Harry La Tour Mlddletown Ohlo A compact strip accumulator and method wherein a [73] Assignee: Armco Steel Corporation, series of guide rollers are arranged to define an archi- Middletown, Ohio medean spiral having a plurality of convolutions, the strip to be accumulated being fed to the inside of the [22] Filed: July 1972 outermost convolution of the spiral, a reverse loop [21] APPL NO: 272,357 formed in the strip so that its leading end extends in the opposite direction and passes to the outside of the outermost convolution of the spiral, the reverse loop, [52] U.S. Cl. 242/55 as Strip is fed into the spiral traveling inwardly i a [51] Int. Cl B65h 17/48 Spiral path between the rollers d fi i consecutive [58] Field of Search 242/55.0l, 55, 78.1 convolutions of the spiral, thereby building up Sets f convolutions of strip of opposite hand interconnected [56] References cued by said reverse loop; and as the strip is removed, the UNITED STATES PATENTS reverse loop travels in the same spiral path in the op- 3,729,144 4/1973 Bijasiewicz 242/55 Potite direction, outwardly, thereby reducing the 3,628,742 12/1971 Fritzsche 242/55 num er f ts f n olu ion of ppo ite hand and 3,506,210 4/1970 La Tour hence the quantity of accumulated strip.

14 Claims, 4 Drawing Figures iATENTEU APR 2 3 1974 'SHEET 1 [IF 2 eW'ENTEU APR 2 3 i974 SHEET 2 BF 2 SPIRAL STRIP ACCUMULATOR AND METHOD BACKGROUND OF THE INVENTION The present inventionrelates generally to strip material flow control, particularly metallic strip, and has to do specifically with a simplified accumulating device particularly suited for. relatively low speed processing lines where appreciable quantities of strip need not be stored to insure continuous operation in the face of discontinuous feeding or discontinuous removal. While various accumulating devices'have hitherto been proposed which may be operated with an intermittent input and continuous output, or vice versa, such devices are relatively complex and are particularly suited to installations where it is desired to accumulate substantial quantities of strip. Generally speaking, they have involved the use ofmechanisms including rotary tables and/r roll cages arranged to build up inner and outer sets of concentric convolutions, the number of convolutions being increased to accumulate strip and decreased when strip output exceeds strip input.

United States Pat. No. 3,506,210, dated Apr. 14, 1970 and entitled Compact Strip Accumulator, teaches an arrangement wherein a length of strip is formed into a coil having an inner set of convolutions and an outer set of convolutions lying in spaced relation to each other, the sets of convolutions being connected by a free reverse loop extending between and joining the outermost convolution in the inner set and the innermost convolution in the outer set. The reverse loop orbits freely in opposite direction between the sets of convolutions as they are rotated, withdrawing strip from the inside of the innermost set of convolutions by rotating the inner set in one direction, and feeding additional strip to the outside of the outer set of convolutions by rotating the outer set in the opposite direction. While such a device is satisfactory, particularly where high speed processing lines are being served and substantial quantities of strip must be stored to insure continuous operation, provision must be made to expand and contract at least the outer roll cage as the sets of convolutions vary in size and consequently the device is relatively expensive.

While the present invention utilizes the conceptof a free reverse loop traveling in one direction to build up a supply of.strip, with the loop traveling in the opposite direction to reduce the supply, accumulation is accomplished by means of rollers defining a simple spiral ratherthan by utilizing inner and outer sets of concentric convolutions. Expansible roll cages are eliminated, and in its simplest form the only moving parts of the accumulator, apart from the sets of rolls which feed the strip to and from the device, are the rollers themselves which are free torotate under the influence of the strip.

RESUME OF THE INVENTION In accordance .with the invention, the accumulator is an extremely simple device, basically comprising nothsuch an arrangement, strip can be accumulated by feeding it to the inside of the rollers defining the outermost convolution, reversing the direction of the strip to form a reverse loop, and passing the reversed portion of the strip to the outside of the outermost rollers for discharge, preferably in-line with its point of entry. As strip is fed into the device, the reverse loop will travel inwardly in a spiral path as defined by the sets of guide rollers, thereby concurrently building up convolutions of opposite hand. Strip will be accumulated at such times as the lineal rate of the strip input exceeds the line'al rate of strip withdrawal. During periods when the rate of withdrawal exceeds the input rate, the reverse loop will move in the opposite direction, i.e., outwardly in a spiral path as defined by the guide rollers, and the number of convolutions will be reduced.

Since the quantity of strip which can be stored will be limited by the number of spiral convolutions defined by the guide rollers, limit switch means may be provided at the termination of the innermost convolution to stop strip input when maximum storage capacity is reached. Similarly, a minimum light switch means may be positionedadjacent the entrance to the outermostconvolution of guide rollers to stop strip withdrawal when the device is effectively empty, i.e., just prior to the withdrawal of the reverse loop from between the guide rollers at the entrance end of the device.

The device may be operated in either the horizontal or vertical position, although if operated in a horizontal position, edge rollers or other supports lying at right angles to the guide roller must be provided to support the strip edge; and consequently, in the interest of simplicity of design and and construction, it is preferred to operate the device vertically, i.e., with the longitudinal axes of the guide rollers horizontally disposed, so that the guide rollers provide the primary support for the accumulated strip.

While particularly suited for use as a simple and inexpensive storage unit for slow speed processing lines, usually feet per minute or slower, the invention also lends itself to other uses wherein it is desirable or necessary to variably control the rate of strip movement. For example, the device may be used as a compact heat treating or annealing furnace. That is, by enclosing the unit in a suitable cover or hood capable of handling elevated temperatures and protective atmospheres, the strip may be held within the furnace for any desired dwell time. Depending upon the size of the accumulator and hence its storage capacity, the operation may be continuous.

Size does not constitute a limitation on the invention and the diameter of the outermostconvolution of the storage cell may vary from as little as 2 or 3 feet to 20 or more feed depending upon the desired storage capacity and the thickness of the strip being accumulated. In working with steel strip, for example, it has been found that the diameter of the free reverse loop should be about 250 times the strip thicknesss, which would constitute the minimum spacing between the guide rollers defining successive convolutions of the spiral.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a somewhat diagrammatic vertical sectional view of the accumulator taken along the line [-1 of FIG. 2.

FIG. 2 is an end elevational view of a simplified accu mulator construction.

FIG. 3 is a schematic elevational view similar to FIG. 1 illustrating the manner in which the strip is initially threaded through the device.

FIG. 4 is a schematic view similar'to FIG. 3 illustrating the manner in which the spiral convolutions are stored, the illustrated condition being maximum storage.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referringfirst to FIGS. 1 and 2, the accumulating device illustrated comprises a base 1 mounting a supporting frame 2 having a pair of side plates 3 and 4 spaced apart by a distance somewhat in excess of the maximum width 'of the strip material to be accumulated. Strip supporting guide rollers 5 extend between the side plates 3 and 4 and arerotatably journaled in the side plates, the guide rollers being arranged to define an archimedean spiral having its center at the point X, as

.seen in FIG. 1. In the embodiment illustrated, the rollers are arranged to define a spiral having three complete convolutions. Since each convolution of the spiral defined by the guide rollers will generate two convolutions of strip of opposite hand, the guide rollers, for the most part, are arranged in pairs, such as the sets 50 and 5b, off-set slightly with respect to each other, so that the strip lying to the inside of any given set will contact only the rollers 5a, whereas the strip. lying to the 'out side will contactonly the rollers 5b. This facilitates free movement'of the rollers since the convolutions of strip contacting the rollers 5a will be of opposite hand and hence movable in the opposite direction from the convolutions of strip contacting the rollers 5b. Single rollers are employed in those areas at the entrance and at the center of the device where oppositely directed movement of adjacent convolutions of strip is not encountered. A set of driven pinch rolls 6 and 7 is provided to feed a length of strip 8 into the device, and a suitable exit roll 9 is provided to help withdraw the strip from the device, it being understood, of course, that withdrawal of the strip will be controlled either by a driven set of exit pinch rolls (not shown) lying beyond the exit roll 9 or by the driven components ofa processing line or the like to which the strip is being fed.

It is also within the spirit and purpose of the invention to drive all or part of the guide rollers to assist in the feeding and withdrawal of the strip, as by driving means 14 seen in FIG. 2. Thus, selected guide rollers may be driven in timed relation to the lineal rate of strip input or strip output, depending upon whether the guide rollers are acting on strip being fed into the device or removed therefrom. Driven guide rollers will reduce friction and, particularly in larger units, may be used to supplement the action of the pinch rolls in feeding the strip and the exit rolls or processing line in withdrawing the strip.

A minimum limit switch 10 is mounted adjacent the entrance of the accumulator, the switch being positioned to detect and arrest strip withdrawal when the accumulator is effectively empty. Similarly, a maximum limit switch 11 is positioned to stop strip input when maximum accumulation is reached. The nature of the limit switch means does not constitute a limitation on the invention and numerous forms of devices may be employed, depending upon the conditions of use. For most applications electrical switches may be employed, although where high temperature conditions are encountered, the switches may be in the nature of a fluidic ear which is effectively insensitive to elevated temperatures.

The initial threading of the device is illustrated in FIG. 3. As seen therein, the strip 8 upon being ad vanced by the driven pinch rolls 6 and 7 enters the accumulator to the inside of the leading guide roller 50, whereupon a free reverse loop 12 is formed in the strip, the strip thus extending in the opposite direction and passing to the outside of the guide roller sets 5a, 5b in the outermost convolution of rollers, the strip exiting from the device upon passage around the exit roll 9.

Upon being threaded in the manner illustrated in FIG. 3, and assuming for the moment that there is no strip output, strip will be accumulated by feeding additional strip into the device. Thus, as seen in FlG. 1, as the strip is fed into the device by the feed rolls 6 and 7, the incoming strip causes the free reverse loop 12 to move counterclockwise in a spiral path between adjacent convolutions of guide roller sets 5a, 5b, thereby forming sets of strip convolutions 8a and 8b which are of opposite hand, the arrows indicating their opposing directions of travel when in motion. It will be understood, however, that the convolutions 8b are not in motion during accumulation, .but rather are laid against the rollers 5b by the action of the reverse loop. As strip input continues, the free reverse loop will continue to move counterclockwise in its spiral path building up additional sets of convolutions 8a and 8b until maximum accumulation is reached, which condition is'illus trated in FIG. 4, at which point the maximum limit switch 11 is contacted to arrest strip input. Each successive convolution of the accumulator spiral, as defined by the guide rollers, results in the storage of two convolutions of strip which are of opposite hand, the convolutions 8a effectively extending in a counterclockwise direction, whereas the convolutions 8b effectively extend in a clockwise direction.

If the accumulator is at maximum capacity, i.e., in the condition illustrated in FIG. 4, and strip input has been stopped, the withdrawal of strip will result in movement of the convolutions 8b in a clockwise direction and, as the strip is payed out, the free reverse loop 12 will move in a clockwise direction and corresponding amounts of strip will be removed from the innermost set of convolutions 8a and 8b. The movement of the convolutions 8a is in the nature of a peeling action when strip is being removed, with the successive sets of convolutions 8a and 8b decreasing proportionately in length as the strip is peeled from convolutions 8a and passes from one side of the reverse loop to the other.

While the foregoing description of accumulator operation has assumed either strip input and no strip output to build up an accumulation of strip, or no strip input and strip output to withdraw the accumulated strip, it will be understood that under normal operating conditions, as where the unit is feeding a continuous processing line, strip will be continuously fed into the accumulator and continuously withdrawn therefrom. If the lineal rate of strip input is equal to the lineal rate of strip output, an equilibrium condition will exist and the free reverse loop will remain stationary, although the entire strip will be in continuous motion, with the convolutions 8a moving in a counterclockwise direction and the convolutions 8b moving in a clockwise direction. When the lineal rate of strip input exceeds the lineal rate of strip withdrawal, the free reverse loop 12 will begin to move in a counterclockwise direction, and additional strip will be accumulated; and conversely, if the lineal rate of strip output exceeds the rate of input, the free reverse loop will move in a clockwise direction. Thus, strip will be built up or accumulated when the lineal rate of travel of the convolutions 8a exceeds the lineal rate of travel of the convolutions 8b, and conversely, the quantity of accumulated strip will be decreased when the lineal rate of travel of the convolutions 8b exceed the lineal rate of travel of the convolutions 8a.

Obviously, the device may be operated manually, with the operator simply stopping or retarding feeding movement when a predetermined quantity of strip has been accumulated, and resuming or accelerating strip feed when the quantity of accumulated strip has diminished to a specified point. As will be apparent to the worker in the art, additional limit control switches similar to the minimum and maximum limit switches 10 and 11 may be employed to effectively balance strip input and output without completely stopping the input or the output. In-addition, a control device 13, such as a photocell, may be located in advance of the pinch rolls 6.and 7 to detect the end of the strip before it reaches the rolls so that additional strip may be added. Such a control device may include means for stopping the pinch rolls while the leadingedge of a new strip is welded to the trailing edge of the preceding strip, and means may be included for stopping the processing line being fed by the accumulator in the event of a breakdown.

As should now be apparent, the instant invention permits the automatic control of strip flow in a processing line or' the like where variable rates of strip movement are encountered. The device is extremely simple and inexpensive, thereby providing a compact device for applications where more expensive and sophisticated accumulating equipment could not be justified.

- Modifications may be made in the invention without departing from the spirit and purpose. Various modifications have already been pointed out and others will undoubtedly occur to the skilled worker in the art upon reading this specification. For example, while in the embodiment illustrated the guide rollers extend between opposing side plates, it will be evident that one or both sides of the device may be open, with the rollers mounted on frame members or brackets, thereby affording the operator a visual indication of quantity of strip in the accumulator. Similarly, various roller arrangements may be employed to support the strip, such as a series of spaced apart rollers on a common shaft,

asopposed to an elongated single roller. While a preference is expressed for sets of rollers, such as the sets 5a, 5b, positioned to be contacted by the strip convolutions 8a and 81:, respectively, single rollers may be employed, particularly in smaller installations, although this will result in a sliding or abrading action when nonequilibrium conditions are encountered.

The embodiments of the invention in which an exclusive property or privilege as claimed are defined as follows:

l. A method of controlling strip material flow which comprises the steps of forming a length of strip into at least a partial set of convolutions of opposite hand, with the innermost ends of said partial set of convolutions interconnected by a reverse loop, accumulating strip by causing said reverse loop to move in one direction in a path of travel defining an archimedean spiral of decreasing diameter, whereby to form sets of spiral convolutions of opposite hand, and withdrawing accumu' lated strip by causing said reverse loop to move in the opposite direction in the same spiral path, whereby to successively remove the accumulated sets of convolutions of opposite hand beginning with the innennost set and working outwardly.

2. The method claimed in claim 1 wherein said strip has a leading end and a trailing end, wherein said reverse loop is caused to move in said one direction by feeding the strip from its trailing end, and wherein said reverse loop is moved in the opposite direction by withdrawing the strip from its leading end.

3. The method claimed in claim 2 including the steps of increasing the quantity of accumulated strip by feeding the strip at a lineal rate of feed in excess of the lineal rate at which strip is withdrawn, and decreasing the quantity of accumulated strip by withdrawing the strip at a lineal rate of withdrawal which exceeds the lineal rate at which the strip is fed.

4. The method claimed in claim 1 wherein the strip material is steel, and wherein the diameter of said reverse loop is at least 250 times the strip thickness.

5. A method of accumulating strip material which comprises providing a length of strip having a leading end and a trailing end, forming a reverse loop in said strip to define strip portions extending in opposite directions, feeding additional strip from the trailing end thereof and guiding said strip in a path of travel defining an archimedean spiral of decreasing diameter, whereby to accumulate strip by forming sets of spiral convolutions extending in opposite directions with each successive set of convolutions being smaller than the preceding set, and decreasing the quantity of accumulated strip by withdrawing the strip from the leading end thereof, whereby to successively remove the setsof convolutions beginning with the innermost set and working outwardly.

6. The method claimed in claim 5 including the step of increasing the quantity of accumulated strip by feeding the strip at a lineal rate of speed in excess of the lineal rate at which strip is withdrawn, and decreasing the quantity of accumulated strip by withdrawing strip at a lineal rate of withdrawal which exceeds the lineal rate of strip feed.

7. In a fiow control device for strip material, a supporting frame mounting a series of guide rollers arranged to define an archimedean spiral having a plurality of convolutions of decreasing diameter, feeding means positioned to feed strip to the inside of the outermost convolution of the spiral defined by said guide rollers, the formation of a reverse loop in the strip between successive convolutions of the spiral causing the portion of the strip in advance of the reverse loop to travel to the outside of the convolutions defined by said guide rollers, and means for withdrawing strip from the outside of the outermost convolution of the spiral as defined by said guide rollers.

8. The device claimed in claim 7 wherein a portion at least of said guide rollers are arranged in coacting pairs and are freely rotatable relative to each other.

9. The device claimed in claim 7 wherein a portion at least of said guide rollers are driven in timed relation to strip movement.

10. The device claimed in claim 7 including limit switch means mounted adjacent the outer and inner ends of the spiral path of travel defined by said guide rollers to control minimum and maximum capacity of said device.

11. A compact strip accumulator comprising a vertically disposed frame having opposing sides lying in spaced apart relation to define a strip receiving opening therebetween, a series of horizontally disposed, rotatable guide rollers extending between the opposite sides of said frame, said guide rollers being positioned to define an archimedean spiral having a plurality of convolutions, the outermost guide roller in said spiral defining the entrance to said accumulator, strip feeding means positioned to feed strip to the inside of said entrance defining guide roller for inward travel to the inside of said guide rollers defining the convolutions of the spiral, the formation of a reverse loop in the strip between successive convolutions of the spiral causing strip ahead of the reverse loop to travel in the opposite direction to the outside of the guide rollers defining the convolutions of the spiral, and an exit roll for withdrawing strip from said accumulator, said exit roll being positioned to receive strip from the outside of one of the guide rollers defining the outer convolution of the spiral, said last named guide roller lying in spaced relation to the outermost guide roller defining the entrance to said spiral.

12. The strip accumulator claimed in claim 11 wherein said guide rollers are freely rotatable.

13. The strip accumulator claimed in claim 11 including means for driving some at least of saidguide rollers.

14. The strip accumulator claimed in claim 10 wherein a portion at least of the guide rollers defining the outer convolution of said spiral, together with the guide rollers defining all but the innermost convolution of said spiral, are arranged in radially offset sets. 

1. A method of controlling strip material flow which comprises the steps of forming a length of strip into at least a partial set of convolutions of opposite hand, with the innermost ends of said partial set of convolutions interconnected by a reverse loop, accumulating strip by causing said reverse loop to move in one direction in a path of travel defining an archimedean spiral of decreasing diameter, whereby to form sets of spiral convolutions of opposite hand, and withdrawing accumulated strip by causing said reverse loop to move in the opposite direction in the same spiral path, whereby to successively remove the accumulated sets of convolutions of opposite hand beginning with the innermost set and working outwardly.
 2. The method claimed in claim 1 wherein said strip has a leading end and a trailing end, wherein said reverse loop is caused to move in said one direction by feeding the strip from its trailing end, and wherein said reverse loop is moved in the opposite direction by withdrawing the strip from its leading end.
 3. The method claimed in claim 2 including the steps of increasing the quantity of accumulated strip by feeding the strip at a lineal rate of feed in excess of the lineal rate at which strip is withdrawn, and decreasing the quantity of accumulated strip by withdrawing the strip at a lineal rate of withdrawal which exceeds the lineal rate at which the sTrip is fed.
 4. The method claimed in claim 1 wherein the strip material is steel, and wherein the diameter of said reverse loop is at least 250 times the strip thickness.
 5. A method of accumulating strip material which comprises providing a length of strip having a leading end and a trailing end, forming a reverse loop in said strip to define strip portions extending in opposite directions, feeding additional strip from the trailing end thereof and guiding said strip in a path of travel defining an archimedean spiral of decreasing diameter, whereby to accumulate strip by forming sets of spiral convolutions extending in opposite directions with each successive set of convolutions being smaller than the preceding set, and decreasing the quantity of accumulated strip by withdrawing the strip from the leading end thereof, whereby to successively remove the sets of convolutions beginning with the innermost set and working outwardly.
 6. The method claimed in claim 5 including the step of increasing the quantity of accumulated strip by feeding the strip at a lineal rate of speed in excess of the lineal rate at which strip is withdrawn, and decreasing the quantity of accumulated strip by withdrawing strip at a lineal rate of withdrawal which exceeds the lineal rate of strip feed.
 7. In a flow control device for strip material, a supporting frame mounting a series of guide rollers arranged to define an archimedean spiral having a plurality of convolutions of decreasing diameter, feeding means positioned to feed strip to the inside of the outermost convolution of the spiral defined by said guide rollers, the formation of a reverse loop in the strip between successive convolutions of the spiral causing the portion of the strip in advance of the reverse loop to travel to the outside of the convolutions defined by said guide rollers, and means for withdrawing strip from the outside of the outermost convolution of the spiral as defined by said guide rollers.
 8. The device claimed in claim 7 wherein a portion at least of said guide rollers are arranged in coacting pairs and are freely rotatable relative to each other.
 9. The device claimed in claim 7 wherein a portion at least of said guide rollers are driven in timed relation to strip movement.
 10. The device claimed in claim 7 including limit switch means mounted adjacent the outer and inner ends of the spiral path of travel defined by said guide rollers to control minimum and maximum capacity of said device.
 11. A compact strip accumulator comprising a vertically disposed frame having opposing sides lying in spaced apart relation to define a strip receiving opening therebetween, a series of horizontally disposed, rotatable guide rollers extending between the opposite sides of said frame, said guide rollers being positioned to define an archimedean spiral having a plurality of convolutions, the outermost guide roller in said spiral defining the entrance to said accumulator, strip feeding means positioned to feed strip to the inside of said entrance defining guide roller (,) for inward travel to the inside of said guide rollers defining the convolutions of the spiral, the formation of a reverse loop in the strip between successive convolutions of the spiral causing strip ahead of the reverse loop to travel in the opposite direction to the outside of the guide rollers defining the convolutions of the spiral, and an exit roll for withdrawing strip from said accumulator, said exit roll being positioned to receive strip from the outside of one of the guide rollers defining the outer convolution of the spiral, said last named guide roller lying in spaced relation to the outermost guide roller defining the entrance to said spiral.
 12. The strip accumulator claimed in claim 11 wherein said guide rollers are freely rotatable.
 13. The strip accumulator claimed in claim 11 including means for driving some at least of said guide rollers.
 14. The strip accumulator claimed in claim 10 wherein a portion at least of the guide rollers defining the outer convolution of said spiral, together with the guide rollers defining all but the innermost convolution of said spiral, are arranged in radially offset sets. 